Exploiting electrochemical biosensing strategies for ethanol determination in yeast fermentation

Ethanol detection is crucial in many research and application fields. Among these the pharmaceutical, clinical and food and beverage industries rely on the quantification of ethanol in fluids. In the pharmaceutical and clinical field, ethanol is detected in biological fluids such as blood, sweat, interstitial fluid and breath. In the food and beverage industry, ethanol detection is fundamental to produce alcoholic beverages. The yeast fermentation process is at the base of alcoholic beverages and other food products. In addition to ethanol, both biological fluids and alcoholic beverages contain glucose. Therefore, it is of great research interest understanding how the detection of ethanol is affected by the presence of glucose. The detection of analytes in solution is generally performed using bulky, expensive and operator-dependent instrumentation. Electrochemical sensors are considered a good alternative to the classic methods as they are portable, less expensive and are characterized by a good sensitivity and low limit of detection (LoD). These sensors are classified in two categories: enzymatic and non-enzymatic. In this thesis both solutions have been investigated by developing Pt-based electrochemical sensors. The significant results of this work are: (i) the effective nanostructuration of Pt screen printed electrodes to enhance the detection performance of the sensor. The roughness factor obtained, which measures the increase of the sensing area, is around 120; (ii) the effective ethanol detection in chloride-free neutral and acidic solution, with and without glucose using non-enzymatic sensor. The sensors exhibited a linear response in the range 0 – 10 mM ethanol (R2 > 0.96). These concentrations of ethanol characterize diluted alcoholic beverages. The sensitivity of the sensor in neutral environment in the absence of glucose resulted to be 145 ± 7 uA/(mM*cm2) with a LoD of 849 ± 43 uM. In acidic environment the ethanol sensitivity was tested in solutions with different glucose concentrations. The sensing conditions that gave rise to the best ethanol detection performance is in the absence of glucose, in which the sensitivity resulted to be 274.188 ± 17 uA/(mM*cm2) with a LoD of 1130 ± 70 uM.